Purlins are struts or beams usually employed in roof decking for supporting the decking or common rafters. They are usually rolled in a variety of transverse or sectional shapes which can be described generally as C, Z, or S shape. A common feature is usually, however, a generally vertical web and usually top and bottom flanges. The flange edges may be subject to further treatment such a further flange or double flange with a flat or bulb fold. The purlins may extend horizontally or at an angle and vary significantly in dimension or gauge. For example, purlins may be from 100 to 300 mm high and have flange widths or extents of from 50 to 80 mm, with treated edges or lips which may be 10-20 mm high. The gauge or thickness may vary from about 1.5 to 3 mm.
It is often desirable to suspend a wide variety of items from purlins, such as piping, wiring conduit, ducts, fixtures or suspending ceilings, with up to about 100 kg static working load. Such items are most often suspended with threaded rod, and with other clips and clamps.
Items are hung from purlins in a number of different ways. One common way is to drill holes in purlins to accommodate fasteners to attach certain types of hangers. The process is labor intensive and requires additional tools (drills, wrenches, screw drivers, e.g.). Such attachments seldom permit adjustment, at least without additional holes, and sometimes drilling is forbidden, especially in lower flanges, which weakens the purlin section, not to mention any coating of the purlin.
Some clips or purlins clamps are available which engage either the lower or both flanges of the purlin. These clips or clamps, while effective, have reduced capacity, particularly with thin gauge purlins. Purlin flanges may be relatively fragile and are meant primarily to add strength and stiffness to purlin sections as a whole. Accordingly, any deformation of the flanges may put the stability of the whole purlin at risk as well as any attachments. It is desirable that the clip load not be at the very edge of the flange since the extent of the flange acts as a moment arm contributing to distortion.
Some clips try to distribute the load to both flanges. While this reduces the risk of deformation, the upper flange is not always accessible even if various heights, dimensions and configurations of flange pans can be met or accommodated. The industry has thus developed a number of hangers which are for specific types of purlins, rather than a universal hanger for many designs of purlins.
It would, therefore, be desirable to have a purlin hanger which did not require holes in the purlin; which did not place a load on the purlin flange, and particularly a load at the edge of the flange; and also which would fit a wide variety of types and sizes of purlins.